[This is adding a new user visible interface so you should be CCing linux-api mailing list. Also CC Hugh for KSM in general. Done now] On Tue 14-05-19 15:16:50, Oleksandr Natalenko wrote: > By default, KSM works only on memory that is marked by madvise(). And the > only way to get around that is to either: > > * use LD_PRELOAD; or > * patch the kernel with something like UKSM or PKSM. > > Instead, lets implement a sysfs knob, which allows marking VMAs as > mergeable. This can be used manually on some task in question or by some > small userspace helper daemon. > > The knob is named "force_madvise", and it is write-only. It accepts a PID > to act on. To mark the VMAs as mergeable, use: > > # echo PID > /sys/kernel/mm/ksm/force_madvise > > To unmerge all the VMAs, use the same approach, prepending the PID with > the "minus" sign: > > # echo -PID > /sys/kernel/mm/ksm/force_madvise > > This patchset is based on earlier Timofey's submission [1], but it doesn't > use dedicated kthread to walk through the list of tasks/VMAs. Instead, > it is up to userspace to traverse all the tasks in /proc if needed. > > The previous suggestion [2] was based on amending do_anonymous_page() > handler to implement fully automatic mode, but this approach was > incorrect due to improper locking and not desired due to excessive > complexity. > > The current approach just implements minimal interface and leaves the > decision on how and when to act to userspace. Please make sure to describe a usecase that warrants adding a new interface we have to maintain for ever. > > Thanks. > > [1] https://lore.kernel.org/patchwork/patch/1012142/ > [2] http://lkml.iu.edu/hypermail/linux/kernel/1905.1/02417.html > > Oleksandr Natalenko (4): > mm/ksm: introduce ksm_enter() helper > mm/ksm: introduce ksm_leave() helper > mm/ksm: introduce force_madvise knob > mm/ksm: add force merging/unmerging documentation > > Documentation/admin-guide/mm/ksm.rst | 11 ++ > mm/ksm.c | 160 +++++++++++++++++++++------ > 2 files changed, 137 insertions(+), 34 deletions(-) > > -- > 2.21.0 > -- Michal Hocko SUSE Labs
